Powered Surgical Device

ABSTRACT

A rongeur-type surgical device incorporating a powered rotary cutting tool having a protective distal foot plate portion which protects against injuring non-target tissue enabling the rapid and safe removal of specifically-targeted bone, cartilage, and soft tissue.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application derives priority from provisional application62/419,170 filed on Nov. 8, 2016, which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates generally to surgical instruments and,more particularly, to improved rongeur-type instruments for cutting orsampling bone, cartilage and soft tissue.

BACKGROUND OF THE INVENTION

A rongeur is a robust surgical instrument with a sharp-edged,scoop-shaped tip, used for gouging out bone. A rongeur can be used toopen a window in bone, often in the skull. It is used in neurosurgery,podiatric surgery, and orthopedic surgery to expose areas for operation.Other common applications for more specialized types of rongeurs, suchas the Kerrison type, include spinal procedures. Common diagnoses forwhich surgeries involving a rongeur include spinal stenosis, spinaltumors, degenerative disk disease, and herniated disks.

Spinal surgery and neurosurgery typically require the surgeon to removetissue such as bone and ligament (“target tissue”) to gain access tounderlying tissue such as dura, nerve roots, intervertebral disc, spinalcord, and brain (“non-target tissue”) so that the intended surgery canthen be performed. As an example, one very common procedure that focuseson discrete elements of the foregoing is a laminectomy in the lumbar,thoracic, or cervical spine, a surgical operation to alleviate acondition known as spinal stenosis. In a laminectomy, a surgeon removesa portion of the vertebrae known as the lamina, usually to give accessto the spinal cord or to relieve pressure on nerves. Currently, in thecase of highly complex procedures such as a laminectomy, it is commonpractice for surgeons to employ two sequential methods to achieveremoval of target tissue. Generally, a surgeon will first utilizehand-held powered drills or burrs to rapidly remove relatively easilyaccessible target tissue. Subsequently, because of the risk of potentialdamage to deeper underlying non-target tissue by a rapidly rotatingdrill or burr, a manual, unpowered surgical tool known as a rongeur isthen applied to remove residual target tissue at a much slower rate.This is done to ensure precise removal of the remaining target tissue,given that the rongeur provides greater precision and control andprotection of non-target tissue because of several design featuresinherent to the conventional rongeur.

The surgery employing the rongeur is performed under constantvisualization. Importantly, the component of a conventional rongeurwhich removes the target tissue is precisely applied via a slidingmechanism, sometimes referred to as a shuttle mechanism, actuated by atrigger or moving handle portion and terminating in a blade or punchmechanism. Additionally, the rongeur includes a protective distal orterminal portion, commonly referred to as a foot plate, that ispositioned between target and non-target tissue. This design aspect of arongeur helps to minimize the chance of damaging non-target tissue.

In using the typical Kerrison-type rongeur, the surgeon must carefullyposition the rongeur between target and non-target tissue, then squeezethe handle to remove a small piece of target tissue, usually between 2-5millimeters. Then the entire instrument is withdrawn from the surgicalsite so the small piece of bone can then be manually removed from thedevice by the surgeon or the surgeon's assistant. The device then mustcarefully be reinserted between target and non-target tissue so that theabove process can be repeated. Depending on the patient's condition,this process may need to be repeated many times over. In such cases, thesurgical procedure is very time-consuming and results in surgical timesthat can take several hours. The duration of the surgery may lead tosubstantial bleeding and prolonged administration of general anesthesiathat can be detrimental to a patient's recovery. A further downside tothe use of such a rongeur is that the repetitive motion may cause handcramping or fatigue on the part of the surgeon, which increases the riskthat a patient may suffer adverse effects from inadvertent tissueremoval or from unintended contact of the rongeur's cutting portion withnerve tissue. These and other issues with the traditional design haveled to numerous alternative approaches to rongeur design.

Various grasping configurations, cutting or shearing designs, andvariations of the two have been proposed to overcome limitationspresented by state-of-the-art commercial rongeurs.

Among the designs introduced in recent years to overcome the issue ofoperator hand fatigue is the Aesculap KAIRison series. This deviceemploys a pneumatic system to obviate much of the need for exertingmanual leverage. A significant limitation presented by the design of thedevice is that it is a Kerrison-type instrument in the form of a bonepunch, rather than a smoothly-operating, precisely controlled rotarytool. As in the case of all other Kerrison rongeurs, the retrieval ofchipped bone or other tissue detritus is necessary after each section oftissue is ablated or otherwise detached.

Another of the designs proposed to address such concerns are U.S. Pat.No. 8,864,766 to Edgar Weaver, issued Oct. 21, 2014, which presents aKerrison rongeur employing a bypasss-cut type shearing mechanism, forspecific cutting and sampling bone, cartilage and soft tissue. Onesignificant limitation of this design is that it will not reliablyremove bone or soft tissue with a high degree of precision, due to thebroad range of action, or throw, of the cutting elements.

Publication US 20040102783, attributed to Sutterlin et al, discloses aPowered Kerrison-like Rongeur system. The device incorporates a poweredcutting element and features a pistol-grip actuator as a design elementwhich appears to be intended to provide an optimized ergonomic effect,but a significant disadvantage manifests itself in the complicatedassembly of the device. Specifically, the instrument is difficult tosterilize as it cannot be immersed in sterilizing solutions, noreffectively autoclaved, due to the complex configuration of varioushigh-speed bearings present in the device.

Other inventors have tried to address the issue of debris collection.For example, a number of various commercially available devices forspinal surgery incorporate integral irrigation and suction feature intissue-removal devices. However, the combination of a powered drill andirrigation or suction mechanisms presently available all feature aninherent limitation, in that the way the irrigation, suction, orcombined irrigation-suction mechanisms are attached to the devices inall cases leads to partial obstruction of the surgeon's view of theoperative field.

A further limitation present in powered devices is that the operator'sability to select from a range of cutting devices is generallyrestricted to the limited choice presented by a single manufacturer'spre-determined selection. As such, a surgeon or medical technician mustchoose from what essentially amounts to a pre-packaged toolkit. Nodevice heretofore has overcome the limitation of the operator not beingable to select from a broad range of powered cutting devices whichessentially snap into place and may be easily switched out for eitheranother identical cutting tool, or replaced by another brand and designof rotary cutting tool.

As demonstrated by the foregoing, there remains a need for an improvedinstrument that can cut bone and tissue, such as with a power-driven,longitudinally displaceable or slideable cutting element or burrdescribed herein to avert the problems associated with conventionallydesigned rongeurs. Such powered elements can include an ability toregulate cutting speed, to actuate the cutting element in such a way asto precisely deploy or retract the burr along a range of motion, and toprovide irrigation as needed, thereby reducing operator fatigue and thetime of the operative procedure and minimizing the risk of damage totissue that need not and should not be removed. Additionally, it may bedesirable to incorporate an optional irrigation function into such arongeur. Embodiments of the present device meet these needs by creatinga robust, easily sterilized, and highly ergonomic powered medicalinstrument capable of incorporating any one of a multiplicity of rotarycutting elements of various designs and manufacture, and featuringoptions such as irrigation, inherent safety features, and presenting theoperator with the ability to remove target tissue to a degree and rateheretofore not possible.

SUMMARY OF THE INVENTION

Embodiments of the present device can provide an ergonomic, poweredsurgical device for safely removing bone and other tissue with a highdegree of precision, concomitantly mitigating operator fatigue.

Embodiments of the present device may also provide a surgical devicecombining the speed of a high-speed burr or drill with the increasedcontrol and safety inherent in the above-mentioned features of therongeur.

Embodiments of the present device may also provide an improved poweredsurgical device substantially similar in basic operation to a standardKerrison rongeur with an ergonomic grip, a positive balance and tactileresponse, an indexable cutting element, and a cutting or ablativesurface which provides for precision in the removal of target tissue.

An additional feature that can be provided in embodiments of the presentdevice is an improved powered surgical device featuring a distinctivelyformed foot plate having an angled, obliquely-rounded exterior face andangled, planar inner face further defined by a central hemisphericalindentation enabling positive engagement with the cutting element at theapex of the throw of the cutting element. Preferably, the interior faceof the foot plate provides for improved cutting, physical ablation, orother mechanical removal by the cutting element of target tissue,whether bone, soft tissue, or other biological material, with minimalconcurrent damage to other surrounding biological material, by providingincreased exposure of the cutting element to target tissue. The angled,obliquely-rounded exterior face presents a smooth profile towards thetarget tissue to make tissue dissection quite easy, with the instrumentproviding functionalities of both a cutting tool and dissecting tool.

Another feature found in embodiments of the present device is to providean improved surgical device with the ability to maintain a relativelystatic position in relation to the operative site. Preferably, thedevice need not be removed or repositioned as frequently as a typicalrongeur since, as in the example of a laminectomy procedure, theresulting bone powder produced by the burr or drill, unlike the chipsresulting from a conventional rongeur, can typically be removed withsuction or a pressurized water jet without the need to withdraw thedevice from the surgical field.

Certain embodiments of the device provide for the rotary cuttingelements to be removably attached to the device to allow the operator toreplace cutting elements as they wear and become dull, and to selectfrom a range of different rotary cutting elements, including differentmanufacturer's rotary cutting elements. As such, a surgeon or medicaltechnician may employ a wide selection of powered cutting elements.

Certain embodiments of the present device feature a handle-mounted drillor burr which may be selected by the operator from a variety of types,including but not limited to standard flat-end burrs to ball mill burrsto a spherical burr, actuated by a trigger, providing a more precise wayfor a surgeon to remove bone or other target tissue. Preferably, thedevice operator, typically a surgeon, can apply varying finger pressureto selectively actuate a trigger to control the speed of the device.

Another objective of the present invention is to further enhance patientsafety by permitting rapid change of cutting elements to avoid continueduse of the same cutting surface (as with Kerrison rongeurs) which willby default become dull from repeated use, thus leading to potentialtearing of non-target tissue such as dura and nerve, ultimately causingpost-operative complications such as dural tears, cerebral spinal fluidleaks, and nerve root injury.

Yet another advantage found in embodiments of the present device is thepossibility of irrigation being substantially immediately and directlyapplied to the operative site. Irrigation is often desirable to minimizethe production of debris such as bone dust, and to prevent heating ofthe bone tissue being operated upon, which otherwise could havedeleterious effects on delicate nerve tissue adjacent to the bonetissue. Current best practices often involve applying irrigationmanually with a bulb syringe to the operative field. This technique isnot precise, and the irrigation fluid may be distributed both in thegeneral location it is needed, as well as adjacent to the operativefocal point, where the instrument is being used. The excess irrigantwill typically be suctioned off the operative field by the surgeon orthe assistant. The present device can incorporate a disposable,detachable irrigation conduit, supplied via an external source connectedto the handle by means of a luer taper-type fitting, which automaticallydelivers irrigant where it is needed at the interface between burr andtarget tissue. The irrigant is directed from the distal end of thedevice at an angle that preferably assures that irrigation will beapplied to where it is needed throughout the movement of the burr.

Various other modifications or features of this device may include theuse of: a trocar at the distal end of the device for penetrating softtissue, a needle, a powered drill, a suction mechanism, a powered drillin combination with a suction mechanism, a powered drill in combinationwith a pressurized water jet, an ultrasonic tip, a bipolar cauteryelement, and a laser, singly or in combination with one or more of theforegoing elements, or some combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary embodiment of the present devicethe entirety of the inventive device.

FIG. 2 is a further side view of the device of FIG. 1, showing withparticularity the tissue cutting assembly fully extended.

FIG. 3 is a perspective view of the device of FIG. 1.

FIG. 4 is a perspective view of the present device, with burr 32 in anextended position and handle 8 retracted or closed position relative tohandle 4, with burr 32 seated in a home position and with handle 8 inopen position relative to handle 4, which in practice leads to a “home”position of burr 32.

FIG. 5 is an exploded view of an embodiment of the present device.

FIG. 6 is a detailed view of two variants of the foot plate 30 furtherillustrating an example of the interior surface of foot plate 30,depicting with a hemispherical indentation 36.

FIG. 7 is a partial side view of an embodiment of the present deviceshowing in greater detail a drive mechanism.

FIG. 8 is a detailed view of an embodiment of the present device moreclearly presenting the removable foot plate embodiment.

FIG. 9 is an elevation view of an embodiment of the present devicedepicting a point of attachment for a supply line.

DETAILED DESCRIPTION

Referring now to the discussion that follows and to the drawings, thepresent device is shown in greater detail. Although the drawingsrepresent some exemplary embodiments, the drawings are not necessarilyto scale and certain features may be exaggerated, removed, or partiallysectioned to better illustrate and explain the present disclosure.Further, the descriptions set forth herein are not intended to beexhaustive or otherwise limit or restrict the claims to the preciseforms and configurations shown in the drawings and disclosed in thefollowing detailed description.

Referring now to FIG. 1, there is shown a rongeur-type device 10consisting of a main handle body 100 composed of interconnected handles4 and 8, a gear 12 which extends from handle 8, actuated in relation toa biasing force imparted by elliptical springs 22 on interconnectedhandles 4 and 8, the biasing force being transmitted through gear 12 torack 72 (not depicted here) to receiver carriage 20, with movablepowered burr shaft 14 rotatably coupled to removable drive motor 18 anda burr 32, a power supply line (depicted in dashed lines) containedwithin motor umbilical retention ring 16 of receiver carriage 20, andlevered shuttle clamps 26 and 28. Movable powered burr shaft 14 cantravel in a reciprocating manner, proximally and distally relative tofoot plate 30 and target tissue as desired by the surgeon along receivercarriage 20 in response to selectively engaging handles 4 and 8 toremove bone or soft tissue, with foot plate 30 providing protectionagainst injury to adjacent non-target tissue.

Referring again to FIG. 1, the motor interface consists of removabledrive motor 18 being coupled to the device by insertion into receivercarriage 20 and secured by levered shuttle clamps 26 and 28. A cuttingelement interface is achieved by coupling burr 32 to the movable poweredburr shaft 14 via a chuck or collet, etc. Irrigant is transmitted fromthe irrigant receiving port 68 at the proximal face of handle 4 toirrigation port 56 via conduit 40, and an external, removable endoscope53 is attached to the device via u-ring 50.

As depicted in FIG. 2, the cutting assembly is fully extended, withhandle 8 in the fully closed position relative to handle 4. The actionof displacing the movable handle 8 in a fixed arc towards the fixedhandle 4 leads to the forward displacement of movable powered burr shaft14 in relation to receiver carriage 20, which leads to the extension ofburr 32 along the range of the throw determined by the degree to whichhandles 4 and 8 are displaced relative to each other changing therelative distance between burr 32 and foot plate 36 in a highlycontrolled manner.

FIG. 3 is a perspective view of the present invention 10 showing allconstituent component constituted together as a complete assembly, withburr 32 in a fully retracted position and handle 8 in the fully open orextended position relative to handle 4. Presented herein is a moredetailed view of levered shuttle clamps 26 and 28 which are in a closedand locked position, securing the assembly consisting of drive motor 18,movable powered burr shaft 14 and powered burr end 32 to the receivercarriage 20. U-ring 50, not referenced in this drawing, providesadditional rigidity to the rongeur by positively engaging with andsecuring powered burr shaft 14 relative to receiver carriage 20. Thepositioning of irrigation port 56 is clearly visible.

FIG. 4 depicts again the complete device assembly, where the main handlebody 100 is slidably connected to receiver carriage 20, with theassembly consisting of trigger-controlled drive motor 18, movablepowered burr shaft 14 and powered burr end 32 as a unit inserted intothe receiver carriage 20 and locked into place with levered shuttleclamps 26 and 28 and further secured by removably-affixed u-ring 50, ina manner permitting actuation of movable handle 8 relative to fixedhandle 4, interconnected with gear 12, by displacing movable handle 8along the path of an arc relative to receiver carriage 20, and engaginggear 12. Movement in the form of the engagement or release of handles 4and 8 is transmitted by the simple linkage to the longitudinaldisplacement of the movable powered burr shaft 14 in receiver carriage20, resulting in extension or retraction of burr 32. Other means ofsecuring the assembly consisting of drive motor 18, movable powered burrshaft 14 and powered burr end 32 such as a modified circlip (notdepicted) are contemplated.

In FIG. 5, in the exploded view the hinge pin 23 providing theinterconnection of handles 4 and 8 is clearly depicted, as are thescrews 17 affixing motor umbilical retention ring to handle 4.

Two additional side views, as depicted in FIG. 6, show in detail twoconfigurations of foot plate 30 with an emphasis on the interior surfaceof foot plate 30, depicting with particularity the hemisphericalindentation 36. The hemispherical indentation 36 provides a positivereceiving point for burr end 32, such that a more comprehensive removalof target tissue is achieved, with the concurrent result being that theexposed cutting face of the device is contained and secured in such amanner as to no longer present an ablative surface to non-target tissue.The distinguishing aspect between the two views is the angle andthickness of the two foot plates, with attendant differences is tissuedissection and tissue positioning outcomes.

In FIG. 7, the interconnection between gear 12 of handle 8 and rack 72,which provides the longitudinal displacement force for moving thecutting element, is depicted in detail.

FIG. 8 shows the positional interrelation between removable foot plate30 and burr 32.

FIG. 9 depicts the irrigation interface created by an irrigant supplyline (not depicted) and the luer taper-type fitting irrigantconstituting receiving port 68 incorporated into handle 4.

The advantages of the present rongeur-type device include, withoutlimitation, unique functional and ergonomic properties permitting thesurgeon to perform the removal of target tissue very efficiently andwith far less muscle fatigue, achieving the desirable results of aconsiderably shortened operative time and a greatly diminished risk ofcramping. A further improvement provided is increased safety presentedby the adjustable burr relative to the protective foot plate 30,affording the surgeon an ability to precisely maneuver the movablepowered burr shaft 14 under direct vision, via a handle-operatedfeature. The rongeur-type device 10 preferably combines the benefits ofthe speed that is achieved with using a high-velocity movable poweredburr shaft 14 driven by interchangeable motor 18 with the precision andsafety features inherent to a standard, manually-operated rongeur.

A further advantage is that unlike a typical Kerrison rongeur, whichmust be removed from the operative field to remove the piece of bone itpunches out every time the handle is depressed, the presently describedrongeur-type surgical instrument may typically stay in a safe positionaway from the nerves, and need not be removed every time a section ofbone is removed. Given that the burr of the present device produces onlybone dust, which is easily suctioned away, the invention reducesoperative time, with attendant diminished bleeding and anesthesia time,and decreases the chance of a nerve injury, thus providing a safersurgery for patients.

Yet another advantage is that the construction of the device permits foran endoscope of either a flexible or rigid type to be securely mountedto the device, thereby providing the surgeon with a clear view of thefoot plate and tissue as it is removed. This feature negates the needfor the surgeon or assistant to manually attempt to keep the surgicalfield in view by manually holding an endoscope. This assures a clearfield of view.

Additionally, the depth of bone or other tissue removal can be preciselycontrolled with the novel design. Moreover, the hemisphericalindentation 36 in the foot plate 30 permits the powered burr end 32 tocompletely remove bone if so desired. This feature also allows for thecontrolled dissection by the powered burr end 32 end of adherent softtissue from the underside of bone. This is particularly advantageous inthe case of spinal surgical procedures known as laminectomies, wheretypically instruments such as curettes or elevators are employed toclear the underside of bone of adherent dura and ligament before aKerrison rongeur is introduced for the removal of bone. In practice, thecombination of the unique design of the foot plate 30 and the poweredburr end 32 permit a surgeon to more precisely and securely avoidunintentional damage to desired nerve or soft tissue which might adhereto the unseen underside of bone.

As such, the entire procedure is safer for patients, who are usuallyunconscious under general anesthesia throughout the surgical procedure.

It should be noted that in one embodiment, the foot plate is removable,allowing the device to function as a handle to precisely manipulate adrill, burr, or other device with the added control of a handpiece aswell as the advantage of irrigation as outlined above when using thefoot plate attached.

It should further be noted that in one embodiment, the foot plate isremovable and replaceable with another, differently dimensioned ordifferently angled foot plate more suited to deeper soft tissuepenetration or dissection.

The above-described embodiments are for promoting an understanding ofthe principles of the invention. It should nevertheless be understoodthat no limitation of the scope of the invention is intended, and thoseof ordinary skill will understand and appreciate the existence ofvariations, combinations, and equivalents of the specific embodiment,method, and examples herein. The invention should therefore not belimited by the above described embodiment, method, and examples, but byall embodiments and methods within the scope and spirit of theinvention.

What is claimed is:
 1. A powered rongeur type surgical instrumentcomprising: a handle with having a movable portion forming an actuator;an elongate receiver carriage coupled to the handle portion, thereceiver portion having a distal end terminating in a foot plateportion; a rotary shaft assembly having a motor interface for receivinga removably mounted motor in said receiver carriage at a proximal end ofthe shaft and a cutting element interface portion at a distal end of theshaft for receiving a rotary cutting element, said rotary shaft beingslidably mounted along a defined rectilinear path along the receivercarriage in response to actuation of the handle for selectivelypositioning said rotary shaft distal relative to said foot plateportion,
 2. The powered rongeur type surgical instrument of claim 1,wherein the foot plate portion further comprises a hemispherical channelsubstantially corresponding to the contour of the cutting element. 3.The powered rongeur type surgical instrument of claim 1 furthercomprising an irrigation port proximate the distal end of the receivercarriage, the irrigation port being coupled to a controllable source ofirrigation fluid and being aligned to apply the irrigation fluid to thecutting element.
 4. The powered rongeur type surgical instrument ofclaim 1, wherein the cutting element interface portion provides forremovably affixing a cutting element to the shaft.
 5. The poweredrongeur type surgical instrument of claim 1, wherein the cutting elementinterface portion is a collet assembly or chuck assembly.
 6. The poweredrongeur type surgical instrument of claim 1, wherein the cutting elementinterface portion is a ratchet-and-detent mechanism.
 7. A poweredrongeur type surgical instrument as claimed in claim 1 wherein saidexternal motor drives said rotary shaft terminating in said cuttingelement, actuated by a trigger mechanism.
 8. A powered rongeur typesurgical instrument as claimed in claim 1 wherein said trigger mechanismis coupled to a selector switch permitting either/or operation of saidexternal motor and irrigation.
 9. A powered rongeur type surgicalinstrument as claimed in claim 1 wherein said receiver carriage bears areceiving fitting for attaching an endoscope.
 10. A powered rongeur typesurgical instrument comprising: a receiver carriage formed as a portionof a handle; a motor retention arm on said handle for engaging aremovable motor; a pinion gear for reciprocally displacing a cuttingelement; and a distal foot plate having a surface forming a first anglewith the vertical and comprising a first cutting element.
 11. A poweredrongeur type surgical instrument as claimed in claim 10 including anelliptical spring mechanism for biasing said handle in a predeterminedposition whereby said cutting element is selectively reciprocated. 12.The powered rongeur type surgical instrument of claim 10 in which adistal terminal foot plate is dimensioned and shaped for a givensurgical procedure.
 13. The powered rongeur type surgical instrument ofclaim 10 where said foot plate bears a hemispherical indentation on theinterior surface capable of receiving said cutting element.
 14. Thepowered rongeur type surgical instrument as claimed in claim 10 wheresaid foot plate is removable, allowing for use rapid change to adifferently-dimensioned foot plate and use of said powered rongeur typesurgical instrument as an ergonomic handle for precisely manipulating adrill, burr, or other device.
 15. A powered rongeur type surgicalinstrument including a handle having a trigger mechanism, a motorremovably mounted in said handle and an elongated receiver carriageconnected to one end of said handle having an upstanding foot plateportion on the end remote from said handle, a cutter attached to saidmotor for rotary motion mounted to said receiver carriage by leveredshuttle clamps, said trigger mechanism being movable in a rectilinearmotion for positioning said foot plate portion relative to and in closeproximity to said cutter, whereby a surgeon orients the target tissue tobe cut between said foot plate portion and said cutter for performingthe surgical procedure.
 16. The powered rongeur type surgical instrumentas claimed in claim 15 including a channel for conveying irrigationfluid.
 17. The powered rongeur type surgical instrument as claimed inclaim 15 whereby said foot plate is dimensioned and shaped for a givensurgical procedure.
 18. A powered rongeur type surgical instrumentincluding a handle having a actuator mechanism, a motor removablymounted in said handle, an elongated tube connected to one end of saidhandle having an upstanding foot plate portion on the end remote fromsaid handle and concentric to and extending through a centralthrough-passage in said annular mounting clamp, a cutter having a burrat the end thereof attached to said motor for rotary motion mounted insaid central through-passage of said annular mounting clamp, saidtrigger mechanism being movable in a rectilinear motion for positioningsaid motor and said cutter relative to and in close proximity to saidfoot plate portion, whereby a surgeon orients the bone or tissueintended to be cut between said foot plate portion and said cutter forperforming the surgical procedure.
 19. The powered rongeur type surgicalinstrument as claimed in claim 18 including a lever arm attached to saidrack and adapted to being displaced by the operator to pivot said rackabout said pinion gear.
 20. A powered rongeur type surgical instrumentas claimed in claim 18 including an elliptical spring mechanism biasingsaid trigger in a predetermined position whereby said cutter ispositioned away from said foot plate.
 21. A powered rongeur typesurgical instrument as claimed in claim 18 where said foot plate isdimensioned and shaped for a given surgical procedure.
 22. The poweredrongeur type surgical instrument as claimed in claim 18 where the distalterminus of the drive shaft is configured to bear a trocar forpenetrating soft tissue.